Computations of Signatures of Coherent Systems with Five Components

The signatures of coherent systems are useful tools to compute the system reliability functions, the system expected lifetimes and to compare different systems using stochastic orderings. It is well known that there exist 2, 5, and 20 different coherent systems with 2, 3, and 4 components, respectively. The signatures for these systems were given in Shaked and Suarez-Llorens (2003 Shaked , M. , Suarez-Llorens , A. ( 2003 ). On the comparison of reliability experiments based on the convolution order . Journal of the American Statistical Association 98 : 693 – 702 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). In this article, we obtain an algorithm to compute all the coherent systems with n components and their signatures. Using this algorithm we show that there exist 180 coherent systems with 5 components and we compute their signatures.     

Properties of Coherent Systems with Dependent Components

We introduce two new families of univariate distributions that we call hyperminimal and hypermaximal distributions. These families have interesting applications in the context of reliability theory in that they contain that of coherent system lifetime distributions. For these families, we obtain distributions, bounds, and moments. We also define the minimal and maximal signatures of a coherent system with exchangeable components which allow us to represent the system distribution as generalized mixtures (i.e., mixtures with possibly negative weights) of series and parallel systems. These results can also be applied to order statistics (k-out-of-n systems). Finally, we give some applications studying coherent systems with different multivariate exponential joint distributions.     

Alternative definitions of bivariate equilibrium distributions

The concept of equilibrium distribution plays an important role in survival analysis, reliability and insurance studies. If we consider the problem of extending this concept to higher dimensions, we do not have a unique solution. In this paper, alternative definitions of bivariate equilibrium distributions are studied and proposed. The Navarro et al. (2006) proposal is considered and some new results are given. We continue with the Gupta and Sankaran's (1998) definition. Necessary and sufficient conditions for its existence are stated and a characterization theorem is given. As a third alternative, a new definition based on conditional specification is introduced and several results are obtained. Reliability properties of the different versions are studied.     

Unemployment in Spain

This article describes the problem of unemployment in Spain and its recent evolution. Data on unemployment in relation to economic growth and some basic demographic characteristics are presented. We also analyze programs designed to reduce unemployment and others to protect unemployed people as different aspects of developing the welfare state in Spain. The framework for analyzing the welfare state is the evolution of industrial relations. Other problems about unemployment are analyzed, including geographical disparities between northern and southern Spain, where rural unemployment is especially severe. We offer an overall perspective on the problem and the government initiatives to ameliorate it.     

Tilamsik: bringing the hospital operating room to the barrio

Tilamsik, organized by the Mary Johnston Hospital's Fertility Care Center, answers numerous requests for vasectomy and laparoscopic sterilization in the remote areas of the Philippines. Literally, Tilamsik means "spark" or "splatter." As the name suggests, the project reaches out to patients who want to be sterilized but cannont come to the center in Tondo. Once the center receives a request, the Tilamsik Outreach Team (composed of 2 doctors, 1 nurse, 1 interviewer, and 1 orderly) immediately scedules the visit. It takes about 2-3 days to pack the sensitive equipment and supplies needed for the trip. The team works closely with the requesting or coordinating agency to make sure that patients are initially screened and properly motivated. Upon reaching its destination, the team can turn any setting into instant operation rooms where the surgical procedure can be performed safely and efficiently. Turover of patients is fast, thanks to the wonders of laparoscpy, a type of endoscopic procedure for tubal ligation. After the operation, the patient rests in a recovery room and waits for the preoperative sedation to wear off, In babout 2 hours she can go home. In the towns and barrios where Tilamsik operates, patients are brought to an improvised recovery room where they lie down on the floor with their own beddings. Traveling in the remote areas is 1 of the major difficulties of Tilamsik. Financial constrants have forced the center to limit the team's trips to places within driving distance form the Tondo center. Tilamsik's services are now made available only up to as far as Lucena and adjacent towns and barrios. With the growing popularity of laparoscopy as a female sterilization technique, the more recent requests for Tilamsik's services are for groups of acceptors numbering from 100-150. To avid duplication of family planning activities, the Tilasik project director has identified areas in the country with laaroscopic sterilization expertise. Project Tilamsik was inaugurated on June 1, 1973 at the Mary Johnstn Hospital. Like other mobile groups, Tilasik was affected as early as 2 years ago by the increasing cost of transportation. Popcom subsidizes the team's trips to provinces around Metro Mala to help the team cope with its transportation problems. Tilasik uses the new generation laparoscope called Laprocator. The unit is more handy and can be used in places where there is no electricity. The number of complications for every 1000 cases reported in a survey of 6871 cases was 116 for persistent pain following surgery, 54 for tubal transection, 32 for hemorrhage, and 22 for infection.     

Some new results on the cumulative residual entropy

The residual entropy function is a relevant dynamic measure of uncertainty in reliability and survival studies. Recently, Rao et al. [2004. Cumulative residual entropy: a new measure of information. IEEE Transactions on Information Theory 50, 1220–1228] and Asadi and Zohrevand [2007. On the dynamic cumulative residual entropy. Journal of Statistical Planning and Inference 137, 1931–1941] define the cumulative residual entropy and the dynamic cumulative residual entropy, respectively, as some new measures of uncertainty. They study some properties and applications of these measures showing how the cumulative residual entropy and the dynamic cumulative residual entropy are connected with the mean residual life function. In this paper, we obtain some new results on these functions. We also define and study the dynamic cumulative past entropy function. Some results are given connecting these measures of a lifetime distribution and that of the associated weighted distribution.     

Characterization of discrete distributions using expected values

In this paper we study characterization problems for discrete distributions using the doubly truncated mean function m(xy)=E(h(X)|x≤X≤y), for a monotonic function h(x). We obtain the distribution function F(x) from m(x,y) and we give the necessary and sufficient conditions for any real function to be the doubly truncated mean function for a discrete distribution.     

Motivational factors and physician advice for physical activity in older urban adults

This study aimed to ascertain by means of a new scale older adults' motives for engaging in physical activity, in a probability and representative sample of an older urban population. The sample size was 630 older adults, ranging from 65 to 94 years in age, randomly selected using multistage sampling. The participants completed a 17-item questionnaire, as well as answering questions on demographic variables, type of demand for physical activity, and physician's recommendation. A principal-component analysis was performed. The relationships among the four factors (physical health, social relationships, competence, and physician's advice) show a clearly motivational structure. Significant relationships have also been found between physician's recommendation and type of demand. The findings suggest that programs promoting physical activity in older adults should have different characteristics from those aimed at general adult populations.